C Program to Implement Bit Array

#include <stdio.h>
 
#define SIZE (58) /* amount of bits */
#define ARRAY_SIZE(x) (x/8+(!!(x%8)))
 
char get_bit(char *array, int index);
void toggle_bit(char *array, int index);
void toggle_bit(char *array, int index) {
    array[index / 8] ^= 1 << (index % 8);
}
 
char get_bit(char *array, int index) {
    return 1 & (array[index / 8] >> (index % 8));
}
int main(void) {
    /* initialize empty array with the right size */
    char x[ARRAY_SIZE(SIZE)] = { 0 };
    int i;
 
    for (i = 0; i < SIZE; i += 2)
        toggle_bit(x, i);
    toggle_bit(x, 56);
    for (i = 0; i < SIZE; i++)
        printf("%d: %d\n", i, get_bit(x, i));
 
    return 0;
}

Output:

0: 1
1: 0
2: 1
3: 0
4: 1
5: 0
6: 1
7: 0
8: 1
9: 0
10: 1
11: 0
12: 1
13: 0
14: 1
15: 0
16: 1
17: 0
18: 1
19: 0
20: 1
21: 0
22: 1
23: 0
24: 1
25: 0
26: 1
27: 0
28: 1
29: 0
30: 1
31: 0
32: 1
33: 0
34: 1
35: 0
36: 1
37: 0
38: 1
39: 0
40: 1
41: 0
42: 1
43: 0
44: 1
45: 0
46: 1
47: 0
48: 1
49: 0
50: 1
51: 0
52: 1
53: 0
54: 1
55: 0
56: 0
57: 0